The Effect of Various Antioxidants on Apple Browning

Photo of reasercher

Researched by Amanda J.


The purpose of this experiment was to compare the color of apples when treated with antioxidants.

I became interested in this idea when I when I read a report my sister did on Tree Top and saw how important keeping the apples fresh was to the industry

The information gained from this experiment could benefit apple production companies increase sales of their products.


My hypothesis was that the AS-1 solution would prevent oxidation most effectively.

I based my hypothesis on the fact that it is the most expensive as well as the fact that it is what Tree Top uses in a commercial process.


The constants in this study were:
•    Storage temperature
•    Time exposed to oxygen
•    Type of apple
•    Labscan EX
•    Storage containers
•    Method of preparation
•    Amount of solution
•    Percent of solution

The manipulated variable was the antioxidant solutions used for the prevention of oxidation.

The responding variable was the color of the apples.

To measure the responding variable, I scanned the color of the apples using a Labscan EX owned by Tree Top’s technical lab.


5 plastic                pitchers
5000 grams          Water
30 grams              As-1
30 grams              Ascorbic acid
30 grams              Calcium ascorbic acid
30 grams              citric acid
1                          cutting board
2                          rubber gloves
1                          apple slicer
1                          apple corer
5                          plastic bags
4                          red delicious apples
1                          Permanent-marking pen
1                          LabScan EX
?                          40ppm proxy acetic acid


 1)    Prepare solutions
    a)    Pour 1000 grams of water into a plastic pitcher
    b)    Add 30 grams of AS-1 to the pitcher
    c)    Stir until dissolved
 2)    Repeat step 1 with Ascorbic acid, Ca-Ascorbic, and citric acid
 3)    Pour 1000 grams of water into a plastic pitcher for the control group
 4)    Core and slice 4 apples
 5)    Treat apples immediately
    a)    Pour 5 slices of apple into the pitcher of AS-1
    b)    Stir for 2 minutes
    c)    Remove apple slices from pitcher
    d)    Put apple slices in plastic bag
    e)    Label plastic bag with the solution
 6)    Quickly, repeat step 5 with each different solution (Ascorbic acid, Ca-Ascorbic, and citric  acid)
 7)    Prep machine by calibrating for pure black and pure white
    a)    Stabilize colors on the LabScan EX
    b)    Change the reading plate to 3/4 inch diameter
 8)    Test apples
    a)    Place one apple slice over the hole in LabScan EX.
    b)    Press F3 on the keyboard
    c)    Remove apple after the machine beeps 3 times
 9)    Repeat step 8 two more times with different slices for same solution
 10)    Repeat step 8 and 9 with each of the different solutions
 11)    Print out data sheet
 12)    Calculate and record averages


The original purpose of this experiment was to compare the color of apples when treated with antioxidants.

The results of the experiment were that AS-1 (Nature Seal) prevented browning most effectively, by the end of testing the lightness level was only on average 45.05 when it started with a lightness level of 46.31.

See the table and graph below.


My hypothesis was that the AS-1 solution would prevent oxidation most effectively.

The results indicate that this hypothesis should be accepted, because As-1 prevented browning most effectively.

After thinking about the results of this experiment, I wonder if the starch content affected how quickly oxidation occurred. I also wondered if there are some types of apples that brown quicker than others. I also wondered if there are other solutions that prevent browning more effectively than AS-1.

If I were to conduct this project again I would test more apples more times. I would also use another method of testing to make sure it was correct.

Apples are a nutritious fruit that most people enjoy. Everyone knows that a cut apple turns brown when it’s left out in the air. Oxidation makes that apple turn brown and most people don’t find that appetizing. There are ways to stop an apple from turning brown.
An apple is a very common fruit. An apple is a healthy snack but to get the full nutritional value of apples you should eat at least one fresh apple every day, like the old saying, “An apple a day keeps the doctor away!” The average person eats about one apple per week. During past studies, eating one fresh apple every day may reduce your risk of getting cancer. A study done in 2001 by the Mayo Clinic showed that apples contain a lot of quercetin and flavonoid, which help prevent the growth of cancer cells. Cornell University did a study that indicated phytochemicals in an apples’ skin reduces the reproduction of colon cancer cells by 43 percent. The National Cancer Institute has studied foods containing flavonoids, which are found in apples. They may reduce the risk of lung cancer by as much as 50 percent.

More than half of all apples grown in the United States for fresh eating come from orchards in Washington State. Selah, Washington is the apple juice capital of the world. The United States produces only 10% of the world’s apples.

Oxidation (O) is when a molecule has a chemical reaction with oxygen (O2). The reaction is when they loose their electrons. We see this happen all the time, when scabs turn brown or when iron rusts. Some foods especially fruit; also turn brown when exposed to oxygen. Oxidation of a fruit is basically a rust-like coating on the surface of the fruit.

Apples float because they are 80% air, which is why when an apple is bruised it turns brown. That happens because the Cells are broken and exposed to oxygen inside the apple. The enzyme that causes oxidation in apples is called “polyphenol oxidase” also known as tyrosinase.
Antioxidants are chemicals that prevent oxidation. Some of the common Antioxidants are vitamins C, vitamin E, vitamin A, and Citric acid.  The most common household antioxidant is Lemon juice (because it contains vitamin C).

No one wants to eat a browning apple. Scientists know there are ways to prevent that. The world needs to know what kinds of things that are used on the apple products they buy.  Apples may be a fruit most people enjoy but they don’t want to eat a bunch of preservatives too. 

Asato, Robert  “Oxidation/Reduction.” January 6th 2005 <>

Baranowski, John Personal Interview

Barden, John A. “Apples.” World Book Encyclopedia. 1998

Hapeman, Cathleen J., “Oxidation.” World Book Encyclopedia. 1998

Kohn, Bernice. Apples a Bushel of Fun & Facts. New York: Parents’ Magazine Press, 1976. pp. 5-55

Saftner, Robert A., et al, “Quality Measurement of Intact and Fresh-cut Slices of Fuji, Granny Smith, Pink Lady, and Goldrush apples.” Journal of Food Science. Volume 70, Number 5, 2005, pp. 317-324

“Why Cut Apples Turn brown”. December 18th 2005 <>


I would like to thank the following people for helping make my project possible:
    My mom for supporting me throughout my entire project.
    My sister for driving me to Tree Top every three days
    Mr. Newkirk for correcting my errors and giving his personal advice
    John Baranowski for his expertise in the preparation and testing of the apples
    Sue Graf for her assistance in John Baranowski’s absence
    Brooke for her help with project ideas and her great attitude as we did our projects

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